An art disclosed here relates to a control apparatus of an engine.
Conventionally, various controls are performed on engines by using an exhaust gas temperature, and for this, the exhaust gas temperature is estimated.
For example, JP2007-533885A discloses a control apparatus of an engine, which estimates a temperature of exhaust gas flowing into a catalyst converter. Specifically, the control apparatus obtains an exhaust gas temperature on a downstream side of a turbine of a turbocharger (i.e., the exhaust gas temperature flowing into the catalyst converter) by determining an exhaust gas temperature on an upstream side of the turbine, obtaining a correction term determined based on an air flow rate and an engine speed, and subtracting the corrected term from the exhaust gas temperature on the upstream side of the turbine.
However, the exhaust gas temperature is influenced by various factors, and with the method of JP2007-533885A, the estimation accuracy of the exhaust gas temperature is not high. For example, in a case of performing a valve overlap in which open timings of intake and exhaust valves are overlapped, fresh air blow-through in which fresh air flows through a cylinder to an exhaust system occurs. The fresh air blow-through is one of the factors which greatly influences the exhaust gas temperature. With the method of JP2007-533885A, the estimation accuracy of the exhaust gas temperature when the fresh air blow-through occurs is not high.